1663490981 has 4 divisors (see below), whose sum is σ = 1674655500. Its totient is φ = 1652326464.

The previous prime is 1663490963. The next prime is 1663490989. The reversal of 1663490981 is 1890943661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1890943661 = 11503 ⋅164387.

It can be written as a sum of positive squares in 2 ways, for example, as 821968900 + 841522081 = 28670^2 + 29009^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1663490981 is a prime.

It is a super-2 number, since 2×1663490981² = 5534404487736684722, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1663490989) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5582036 + ... + 5582333.

It is an arithmetic number, because the mean of its divisors is an integer number (418663875).

Almost surely, 2^1663490981 is an apocalyptic number.

It is an amenable number.

1663490981 is a deficient number, since it is larger than the sum of its proper divisors (11164519).

1663490981 is a wasteful number, since it uses less digits than its factorization.

1663490981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11164518.

The product of its (nonzero) digits is 279936, while the sum is 47.

The square root of 1663490981 is about 40785.9164540899. The cubic root of 1663490981 is about 1184.8775843681.

The spelling of 1663490981 in words is "one billion, six hundred sixty-three million, four hundred ninety thousand, nine hundred eighty-one".